1. Field of the Invention
The present invention relates to an ink-jet recording apparatus for recording data on a recording medium by ejecting ink thereon, as well as an ink-jet recording method, and more particularly to an ink-jet recording apparatus and method for recording data through making the color element of ink insoluble or coagulated.
2. Description of the Related Art
It is gradually getting known that a conventional ink-jet recording apparatus adopts recording liquid such as ink (hereinafter may be referred to just as ink), and processing liquid that reacts with the color element in ink and makes it either insoluble or coagulated, with a view to improving the water-resisting property and image quality thereof. The processing liquid is crystal clear, and is mixed with ink by ejecting on or to a nearby area of ink to generate the above-mentioned reaction. By using such processing liquid, the color productivity and water-resisting property of ink fixed on a recording medium is improved, and generation of bleeding phenomenon can be avoided. Specially in a case in which a recording medium which is not coated with ink-receiving layer or the like is used, in other words, a widely diffused normal paper sheet or the like is used, a data recording free of bleeding is enabled and a great effect can thus be obtained.
By the way, when ink is ejected, there are occasions that a satellite ink drop is generated following the main drop thereof, and it is also conventionally known that in such a case, if the ejecting direction or angle of the main ink drop and that of the satellite ink drop is different from each other, an adverse effect is caused to the printed result.
FIG. 5 is an exemplary view that indicates a state in which ink is being ejected, and explains the difference between the ejecting direction and angle of the main drop and those of the satellite drop. As shown in FIG. 5, a bubble 4 is generated by rapidly heating up a heater 3 provided in the liquid flowing path of the recording head, and the main drop D1 is ejected in due course. Thereafter, when the meniscus of ink recedes in accordance with collapse of the bubble 4, the satellite drop D2 is generated. Generally, ejecting speed of satellite drops is slower than that of main drops. Also, as shown in FIG. 5, if the meniscus recedes in somewhat an eccentric manner due to the shape of an ejection nozzle, the satellite drop is ejected in the direction H2 which is different from the direction H1 in which main drop is discharged. In this way, the main and satellite drops, whose ejecting speeds are different from each other, are generated.
As explained heretofore, when a reciprocal printing is performed by scanning the recording head in each of the both rightward and leftward directions in a state that the ejecting speed and angle of the respective main drop and satellite drop are different, the following problems are likely to occur. Note that the rightward scanning may be referred to as normal scanning, and the leftward scanning may be referred to as reverse scanning throughout the present specification.
FIG. 3A shows a state in which the ejecting direction of the satellite drop is converted to the direction which is opposite to the scanning direction with respect to the main drop ejecting direction. In this case, since the offset of the scanning direction of the recording head and that of the satellite drop is opposite to each other and the ejecting speed is thus slow, the satellite drop Da2 is more affected by the scanning speed than the main drop Da1 is. Accordingly, the direction of the main drop and that of the satellite drop become substantially the same, and are dropped onto the substantially same positions Da1' and Da2' on the recording medium in a superimposed manner. That is, the offset of the ejecting direction of the satellite drop with respect to the main drop is compensated by the scanning speed of the recording head.
On the other hand, as shown in FIG. 3B, when the recording head is scanned in the reverse direction, in other words, when the ejecting direction of the satellite drop is converted to the same direction as that of the scanning of the recording head with respect to the main drop ejecting direction, the satellite drop Db2 whose speed is rather slow is likely to receive the effect of the reverse scanning speed of the recording head than the main drop Db1 receives, whereby the offset between the ejecting direction of the main drop and that of the satellite drop during the printing operation becomes substantially more expanded, and they fall, in fact, on two distinctly different points Db1' and Db2' on the recording medium 2. On this occasion, the dots printed on the respective two different points appear, as shown in the lower section of each of FIGS. 3A and 3B, as of different size and shape, and as a result they appear in different size of character as a whole, causing thereby a problem in its printing quality.
In order to solve the problems aforementioned, there has been proposed so far a method for equalizing the ejecting direction of the both main drop and satellite drop through modification of shape of the record liquid flowing path, or by correcting the angle and/or the position of the orifice provided in the recording head. However, due to the above corrections, the ejecting angle is varied as a whole, and accordingly the dot forming positions become different per each nozzle row, and also size of the orifice area is made smaller and so forth. Further, even though the ejecting directions of the main drop and that of the satellite drop are equalized, correction of the difference in the ejecting speeds thereof is theoretically difficult, and thus there has been an attempt to avoid the positional difference between the dot formed in the normal scanning of the recording head and that formed in the reverse scanning, for example by inclining the recording head or the like, in order to make the dot shapes thereof substantially the same, which, however, was not totally available as the total cost was thereby increased.
Apart from the above-explained problems caused during the reciprocal scanning of the recording head for printing, there has also been such a problem that in a case in which both processing liquid and recording liquid (or ink, in this case) are used for printing operation, and the recording head is provided with only one nozzle row, in one of the reciprocal scanning movements, the processing liquid is ejected before ink (which is called "primary ejection" of the processing liquid), whereas in the other movement, ink is ejected before the processing liquid (which is called "secondary ejection" of the processing liquid). In the case of the secondary ejection, since ink as the recording liquid is ejected first, the dot formed thereby is often blurred with ink, and thus becomes larger than that in the case of the primary ejection, which is explained with reference to FIGS. 4A and 4B.
FIG. 4A shows the case in which ink is ejected before the processing liquid (namely, the secondary ejection), while FIG. 4B shows the case in which the processing liquid is ejected before ink (namely, the primary ejection). In FIG. 4A, ink is first ejected as shown in (a), but it is spread before ejection of the processing liquid as shown in (b) because of its high permeability. Thereafter, the processing liquid is ejected as shown in (c), and the dot is thereby fixed finally as shown in (d). The diameter of the dot formed by these procedures is shown in the lower part of FIG. 4A. Contrary to this, as shown in FIG. 4B, the processing liquid is first ejected as shown in (a), but it is not spread so much because of its smaller dot diameter and lower permeability than those of ink. Thereafter, ink is ejected thereon as shown in (b), and the dot is thereby fixed finally as shown in (c). The diameter of the dot formed by these procedures is shown in the lower part of FIG. 4B.
As is obvious from the difference in diameters of each dot by FIGS. 4A and 4B, the dot diameter is formed differently depending on which of the processing liquid and ink is ejected first. This is one of the reasons for the difference in printed results, namely, the difference in the size of character letters or the like, caused by the normal scanning and by the reverse scanning.
In order to solve the aforementioned problems, there has been proposed a method in which the permeability of ink is suppressed. However, if this method is taken, a such problem that fixing characteristic of ink is deteriorated and ink is thus likely to become solid and so on have been caused. There has been proposed also a method in which ink and processing liquid are discharged from two nozzle rows, but was not completely available either because of an increase in cost.